1. Field of the Invention
The present invention relates to a device for supporting a payload in a launch vehicle for launching said payload, said launch vehicle including a shell supporting at least one booster which in operation applies excess forces to said shell, said device including a system for mechanically connecting said payload to said shell of the launch vehicle.
2. Description of the Related Art
This kind of device is disclosed in applicant""s international patent application WO 98/32658, corresponding to U.S. Pat. No. 6,244,541, with issue date of Jun. 12, 2001. It is designed to be integrated into a launch vehicle for launching a payload into space, shown diagrammatically in FIG. 1 of the accompanying drawings, in which the launch vehicle includes a first stage 1 equipped with boosters 2 and 3 fixed to the shell 1a of the first stage in diametrally opposite positions and parallel to the longitudinal axis X of the shell. FIG. 1 also shows diagrammatically a payload such as a satellite 4 mounted on the shell 5a of a second stage 5 of the launch vehicle by means of an adapter in the form of a frustoconical skirt 6. The satellite is conventionally protected by a nose-cap 7 while passing through the atmosphere. The shells 1a and 5a are cylindrical, co-extensive and fastened together.
As explained in the patent application previously cited, the thrust developed by the boosters 2, 3 applies high axial forces to the shell 1a of the first stage, in particular at the points 8, 9 at which the boosters 2, 3 are attached to the first stage. FIG. 2 of the accompanying drawings shows the intensity F of these forces as observed at the periphery of the shell 1a. 
The forces are much more pronounced at the attachment points 8, 9 (at angular positions of 90xc2x0 and 270xc2x0, respectively) and it they were transmitted to the skirt 6 via the shell 5a of the second stage 5 they would cause asymmetrical deformation of the skirt, which could damage the satellite if no countermeasures were applied. FIG. 3 of the accompanying drawings shows in cross section the xe2x80x9cdeformationxe2x80x9d of the shell of the launch vehicle subjected to the distribution of forces shown in FIG. 2 by boosters 2, 3 fixed to the shell at points 8, 9, respectively.
According to the patent application previously cited, transmission of deformation to the satellite is prevented by installing between the satellite and the launch vehicle, for example at the level of the larger base 6b of the skirt 6, whose other base 6a receives the satellite, a suspension device consisting of an annular chamber with flexible walls and filled with a fluid. The xe2x80x9cexcessxe2x80x9d forces received by the annular chamber in line with the attachment points 8, 9 are uniformly distributed circumferentially by the fluid in the chamber and the skirt 6 is therefore subjected to perfectly symmetrical forces that do not deform the skirt asymmetrically. The integrity of the satellite is therefore protected while the boosters 2, 3 are operating.
Means are provided for varying the pressure of the fluid contained in the annular chamber. Thus the pressure can be lowered from a relatively higher value ensuring good mechanical cohesion of the launch vehicle and the skirt 6, as is necessary in particular when the boosters 2, 3 are operating, to a relatively lower value for filtering forces such as vibration or shock forces propagating in the launch vehicle, in particular at the time of separation of stages of the launch vehicle and the nose-cap 7.
The device described in the patent application previously cited achieves the stated objective. However, it implies the use of either an annular chamber with flexible walls or a chamber with two complementary rigid annular walls mobile axially relative to each other, the chamber being sealed by at least one O-ring whose length is equal to the circumference of the chamber.
Because it is integrated into a launch vehicle, this kind of device must be very reliable. It can be very costly to achieve this because of the sealing problems that arise when using an annular chamber with flexible walls or an annular chamber incorporating an O-ring with the same circumference.
If the annular chamber with flexible walls solution is adopted, the flexible wall is greatly stiffened when the pressure in the chamber is high, to the point where forces transmitted by the device pass through the wall rather than through the fluid that it confines, which renders the device ineffective at high pressures.
One object of the present invention is precisely to provide a device for supporting a payload in a launch vehicle for launching said payload into space that is free of the above drawbacks and which in particular prevents the transmission of excess forces from the launch vehicle to the satellite, combined with highly reliable operation and moderate production cost.
The above objective of the invention, and others that will become apparent in the course of the following description, are achieved with a device for supporting a payload in a launch vehicle for launching said payload, said launch vehicle including a shell supporting at least one booster applying excess forces to said shell when in operation, and said device including means for mechanically connecting said payload to said shell of said launch vehicle, characterized in that said connecting means are designed to ensure mechanical coupling of the load and the shell in the direction of a longitudinal axis of the launch vehicle and decoupling thereof in radial and tangential directions.
As will be seen later, the connecting system prevents significant transmission of excess forces to the payload whilst ensuring mechanical cohesion of the launch vehicle/payload combination.
In one preferred embodiment of a device in accordance with the invention, the connecting means include an annular rim fastened to said payload and an annular groove fixed with respect to said shell, accommodating said rim so that is able to slide in any radial direction or tangential direction, and stopping any movement of said rim relative to said groove in the axial direction.
In accordance with another feature of the device in accordance with the invention, the connecting means further include at least one thrust bearing system mechanically connecting the shell and the payload in at least one of said radial and tangential directions. The thrust bearing system is at a node of the deformation of said shell in the presence of excess forces in cross section in a plane passing through said thrust bearing system. It is even more preferable for the thrust bearing to be disposed at a displacement node of said shell in a tangential direction and therefore in a tangential direction passing through that node.